The present invention relates to improvements in methods of and in apparatus for making tobacco rods. More particularly, the invention relates to improvements in methods of and in apparatus for making one or more continuous rod-like bodies, called fillers, which can be converted into tobacco-containing parts of plain or filter cigarettes, cigars, cigarillos or analogous smokers' products.
It is well known to make the rod-like filler of a cigarette by showering particles of tobacco (such as shreds of tobacco leaf laminae) which is supplied by a so-called distributor or hopper onto the exposed side of a running sieve-like endless foraminous belt while the other side of the belt travels along the open side of a stationary suction chamber. This results in conversion of the shower into a stream which contains a surplus of tobacco particles and moves lengthwise with the belt past a trimming or equalizing device which removes the surplus. The resulting rod-like filler is confined in a running continuous web of cigarette paper or other suitable wrapping material to form therewith a continuous rod which is severed at regular intervals to yield a succession of plain cigarettes of unit length or multiple unit length. Such products are ready to be confined in packs or to be provided with filter mouthpieces to form therewith filter cigarettes of unit length or multiple unit length. The making of plain or filter cigarillos, cartridges, cigars or analogous smokers' products involves or can involve procedures or steps similar to those involving the making of plain or filter cigarettes. Conventional machines for the making of plain and filter cigarettes are disclosed, for example, in U.S. Pat. No. 4,281,670 granted Aug. 4, 1981 to Heitmann et al. for “APPARATUS FOR INCREASING THE PERMEABILITY OF WRAPPING MATERIAL FOR ROD-SHAPED SMOKERS' PRODUCTS”.
It is also known to segregate particles of tobacco dust or analogous less desirable fragments of smokable material from the much more desirable elongated shreds of tobacco leaf laminae and/or from the atmosphere in a cigarette making plant. The thus segregated particles can be utilized for the making of sheets or films of reconstituted tobacco. Alternatively, such less desirable particles of dust or the like can be introduced into the tobacco stream which is borne by the foraminous belt; such introduction takes place prior to removal of the surplus, i.e., prior to conversion of the tobacco stream into a rod-like filler. The purpose of such introduction of tobacco dust and/or like particulate material into the tobacco stream is to contribute to the weight, bulk, density, “feel” and/or other desirable characteristics of smokers' products embodying lengths of the filler. It is normally preferred to remove all or practically all particles of tobacco dust from the shower or showers of tobacco particles (normally shreds) which are being conveyed to the stream-forming station.
It is equally known to evacuate from the aforementioned suction chamber of a cigarette rod making machine all or practically all particles of tobacco dust. The term “dust” is intended to embrace all such particles of tobacco and/or foreign matter entrained by full-sized tobacco shreds which do or can consist of a smokable material but are often too small to allow for appropriate interlacing with genuine tobacco shreds. The thus gathered particles of tobacco dust, as well as relatively small or very small shreds, are admitted into the tobacco stream.
It is further known to simultaneously produce a plurality of (particularly two) continuous cigarette rods each of which yields a series of plain cigarettes of unit length. Reference may be had, for example, to commonly owned U.S. Pat. No. 5,125,419 granted on Jun. 30, 1992 to Heitmann for “METHOD OF AND APPARATUS FOR MAKING PLURAL TOBACCO STREAMS”. Such arrangement multiplies the output of the cigarette making machine with two or more foraminous tobacco rod making conveyors.
As a rule, the aforementioned suction chamber is adjacent that side of an endless foraminous belt or the like which is disposed opposite the side serving to gather a stream of tobacco shreds. The suction chamber is apt to accumulate substantial quantities of tobacco dust within a relatively short interval of time. Such dust normally contains very small particles of tobacco leaves which normally adhere to the adjacent tobacco shreds on their way to the rod forming station but become separated from the shreds during the next-following processing of cigarettes of unit length or multiple unit length. The dust in the plenum chamber further contains minute particles of sand and/or rock as well as relatively small tobacco fragments which are more likely to be interlaced with desirable tobacco shreds of standard size and/or shape and which are less likely to readily penetrate through the openings of the endless foraminous belt.
The relatively small tobacco fragments develop in part during the making of tobacco shreds and in part during transport of shreds from the shredding station to the rod forming station, particularly during transport toward the foraminous belt. Some of the small fragments even penetrate into the openings of the foraminous belt and gather in the suction chamber. Additional relatively small tobacco fragments develop during transport of satisfactory shreds with the foraminous belt; thus, the end portions of a certain percentage of shreds penetrate into the openings of the belt to be sheared off the major portions of the respective tobacco shreds during separation of the respective portions of the tobacco stream from the foraminous belt.
In accordance with heretofore known procedures, all solid particles which happen to penetrate into the suction chamber are evacuated from the chamber with the air stream which enters the chamber by way of openings in the foraminous belt, which flows through the chamber, and which is evacuated by way of one or more outlets. The thus evacuated air is caused to flow into a central dedusting station of the entire cigarette making plant and the thus accumulated mass of dust and minute or relatively small tobacco shreds is thereupon converted into sheets or other configurations of reconstituted tobacco. Such procedure must be carried out by resorting to bulky and costly machinery and is expensive in spite of the fact that the reconstituted tobacco can be or is being reused for the making of smokers' products. For example, the sheet can be shredded and the thus obtained shreds are admixed to the shreds of the shower (i.e., to the shreds which are obtained as a result of comminution of tobacco leaf laminae).
U.S. Pat. No. 3,282,270 (granted Nov. 1, 1966 to Morris et al. for “TOBACCO-MANIPULATING APPARATUS”) discloses a method which involves segregation of tobacco dust directly at the cigarette rod making machine and immediate pneumatic reintroduction of separated dust into the shower of tobacco shreds advancing toward the foraminous belt of the pneumatic conveyor which converts the shower into a continuous tobacco stream. The introduction of dust into the shower is to be carried out by the shreds which constitute the shower, and retention of dust in the stream is to be effected by those shreds which already adhere to the exposed side of the foraminous belt.
A drawback of the just described patented proposal of Morris et al. is that only the relatively large particles of dust are intercepted by tobacco shreds at the foraminous belt. All or nearly all small particles of tobacco dust, sand and other foreign matter are free to reenter the suction chamber so that the air stream issuing from the suction chamber contains a continuously increasing percentage of dust and foreign matter. It is to be borne in mind that the shower of tobacco shreds contains and delivers to the tobacco stream forming station additional particles of tobacco dust, sand and other minute particulate material and that, sooner or later, all or nearly all such particles enter and circulate with the air stream which delivers the solid contents of the suction chamber to the shower of tobacco shreds advancing toward the foraminous belt.